Crystallization method for oxide semiconductor layer, semiconductor device manufactured using the same, and method for manufacturing the semiconductor device

A method for manufacturing a semiconductor device, the method comprising:

• a first step of forming a gate electrode on a substrate;
• a second step of forming a gate insulating film over the substrate, to cover the gate electrode;
• a third step of depositing an In—Ga—Zn oxide over the gate insulating film while heating the substrate to a temperature of 200 to 300° C., wherein an atomic percent ratio of Zn in the In—Ga—Zn oxide as-deposited is higher than each atomic percent ratio of In and Ga;
• a fourth step of heat-treating the deposited In—Ga—Zn oxide at a temperature of 200 to 350° C., thereby forming an active layer crystallized throughout an entire thickness of the active layer;
• and
• a fifth step of forming a source electrode and a drain electrode, which contact opposite sides of the active layer, respectively.